The invention relates to a pump for the transporting of fluids and/or of mixtures of fluids with a proportion of solid material, comprising a housing and at least one restrictor gap seal which is provided in the housing to reduce the pressure in a restrictor gap along a rotatable part of the pump.
Centrifugal pumps are also used for the transporting of fluids and of mixtures of fluids with a proportion of solid material such as multiphase mixtures of oil, gas, water and sand, such as occur in the transporting of crude oil and natural gas. Such a pump includes a pump shaft fitted with impellers, which are rotatably arranged in a housing, as well as a relief piston for the axial thrust compensation which is connected to the pump shaft such that it rotates along on the rotation of the pump shaft. So that the pump shaft and the relief piston are freely rotatable in the housing and, on the other hand, pressure compensation flows along the rotatable parts are limited, restrictor gaps are formed between the housing and the pump shaft or the relief piston respectively. Furthermore, restrictor gap seals are provided in the pump to reduce the pressure in the restrictor gaps along the pump shaft or along the relief piston respectively and to reduce the gap losses associated with the pressure compensation flows in this manner.
The embodiments of restrictor gap seals used in conventional pump construction include, for example, smooth restrictor gaps with a small gap width, restrictor gaps with labyrinths, restrictor gaps with radial sealing rings, with quench seals, floating-ring seals, different embodiments of face seals or packs. The restrictor gap seals of the prior art all have their specific disadvantages; e.g. the leakage amount of the smooth restrictor gap is relatively large, the clearance between the housing and the rotatable parts is critical and the comparatively long construction of the smooth restrictor part is irritating. It is disadvantageous in the face seals that they are of complex design and react sensitively to changes in temperature and rotational speed. In pumps with multiphase mixtures, in particular multiphase mixtures with a proportion of solid material, there is a further difficulty in that the abrasive effect of the solids has a noticeable effect on the service frequency and service life of the restrictor gap seals.